A federal appeals court has blocked an attempt to delay David Earl Miller's execution while he challenges the constitutionality of lethal injection and the electric chair.

In an opinion handed down Monday, the 6th Circuit Court of Appeals sided with the federal district court in Nashville, saying Miller's execution should move forward as scheduled Dec. 6 while his lawsuit against Tennessee's execution methods is pending.

In order to secure a stay of execution, the appellate judges wrote, Miller would have to show he was likely to succeed in challenging Tennessee's lethal injection and electrocution methods as unconstitutionally cruel and unusual.

A majority of the judges said he had failed to do so.

"Miller (has) not shown that the new (lethal injection) protocol is 'sure or very likely' to be less humane than electrocution" the majority wrote in a 2-1 decision. "Because Miller has elected to be executed by electrocution, he has waived any challenge to his execution by that method."

But Judge Helene White dissented, saying he had shown adequate evidence that the state's lethal injection and electrocution methods were cruel and unusual enough to violate the U.S. Constitution.

The defeat at the 6th Circuit further limits Miller's options to stop his execution, although a few remain.